In existing fence systems, common baluster installing methods are relatively complex and cumbersome. Some requires to weld on site a baluster to an upper rail and a lower rail, however appearance treatment are needed after welding. Some involves fabricating a plurality of balusters into a whole piece, and then splicing the same on site, but the whole rail structure is large in volume and unadjustable in the splicing size. These bring great trouble to on-site installation and need great human and material resources.